Hacking a remote-controlled moth with insect venom

Researchers use microfluidics to control the metabolism of a moth, opening up …

There is just so much going on in science that no single person can keep up with it all. So when a friend of mine sent me a copy of an article about the beginnings of a remote-controlled moth, I just had to write about it. One problem though—the research paper is from August of last year, so there may be some bemusement on the part of the researchers that the media has cottoned on to their research so late. What can I say? I don't go looking for remote-controlled moths, I wait for them to come to me.

This research comes under the heading of micro-air-vehicles development, and it turns out that building tiny airplanes is quite difficult. This is, in large part, due to the joys of momentum. A large aircraft has a lot of mass, so the conservation of momentum turns every breath of turbulence and minor change in air pressure into minimal changes in altitude, attitude, and speed.

But this is not so for tiny vehicles. Designing control systems and electronics that can manage a vehicle that can be turned upside down by someone sneezing is probably possible. Fitting those electronics into the vehicle is not. Even running the whole shebang remotely is difficult, due to the sensor and data transfer requirements. As a result, some in the field are turning to nature's micro-air-vehicles—insects—and gazing with admiration at their abilities. Insects face all the same problems, but get around them by having a complex and highly variable wing-stroke pattern that compensates for (bad pun alert) on-the-fly turbulence.

And this is where things turn a bit surreal, with researchers discussing the carrying capacity, air-speed velocity, and range of various moths. (You have to provide your own coconuts and mockery-filled castle though.) It turns out that the Tobacco hornworm moth is the ideal insect to turn into your own micro-air-vehicle. It's big, so it can carry quite a bit of excess weight without adversely affecting its flight characteristics. It has a range of several kilometers and, for an insect, is quite quick. But how to control it?

Well, in this case, the researchers chose to directly manipulate the metabolism of the moth. They injected adult moths with a collection of insect venom, spider venom, and man-made insecticides to examine the effect on the moth's metabolism. From these experiments, they found that several of the venoms could be used to reversibly slow the moth's metabolic rate—depending on the amount injected, the venom could act locally or globally.

From there, the researchers moved on to testing a remote controlled injection system. Before the adult moth emerged from its pupal stage, they cut it open, inserted a microfluidic device, and then literally glued the moth closed again. Most moths survive this process, but not all of them wound up with unrestricted wing motion.

The researchers tethered the viable moths in a chamber with an agitator that kept them flying. When the microfluidic injection process was activated, it slowed the moth's metabolism. The moth could be slowed down by a chosen amount—to the point where they could induce paralysis in the moth and then reanimate it.

Of course, this doesn't allow the researchers to control where the insect flies to, nor does it induce the insect to fly at all. But, with a more complicated microfluidic injection system, the metabolic rate of each wing could be used to control direction, while an electrode could be used to stimulate the insect's flight response.

Now, this sounds rather complicated—surely if you can stick a microfluidic device in a moth, you could directly control the wings with electrodes? It turns out that you can, but you end up having to control every aspect of the flight, which is not all that desirable.

This may turn out to provide a compromise, where the controller can control the general direction of the flight—perhaps not very precisely—or prevent the insect from having a wee rest on a branch. And that is certainly much better than nothing.

I realize that the start of this article took a rather lighthearted tone, which could be interpreted as poking fun that the research and researchers. It is, sometimes, hard not to see the inherent comedy associated with an outsider's perspective on research. But that doesn't take away from the achievements of the researchers: this is a very impressive demonstration of the understanding and control of metabolism in this particular moth species. Nevertheless, I can't help picturing a future in which urban terrorists come packing fly spray.

Chris Lee / Chris writes for Ars Technica's science section. A physicist by day and science writer by night, he specializes in quantum physics and optics. He lives and works in Eindhoven, the Netherlands.